Telephone-exchange system.



No. 697,993. Patented Apr. 22, |902.

W. M. DAVIS.

TELEPHONE -EXCHANGE SYSTEM.

(Application filed Aug. 16, 1901.)

(No Model.)

"WILLIAM M. DAVIS, OF CHICAGO, ILLINOIS, ASSIGNOR CARLSON TELEPHONEMANUFAC TO TI-IE STROMBERG- TURING COMPANY, OF CHICAGO, ILLI- NOIS, ACORPORATION OF ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

SECIFICATON forming part of Letters Patent No. 697,993, dated April 22,1902. `Application tiled August 16, 1901. Serial No. 72,256. (No model.)

To all whom, t may concern:

Be it known that I, WILLIAM M. DAVIS, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Telephone-ExchangeSystems, (Case No. 22,) of which the following is a full, clear,concise, and exact description, reference being had to the accompanyingIo drawings, forminga part of this specification.

My invention relates to telephone-exchange systems, and has for itsobject the provision of improved means for supplying the operator withsupervisory signals, each signal corresponding to a connectedsubscriber.

Heretofore it has been proposed to employ supervisory signals eachassociated with a telephone-line and so arranged in each cordcircuit incombination with a condenser that 2c the apparatus at each of the twoconnected subscribers7 stations is adapted to effect the control of thecorresponding supervisory relay or signal, each signal servingaccurately to indicate the condition of the corresponding lineindependently of any other apparatus than the apparatus at thecorresponding substation, the two signals thus associated with eachcord-circuit indicating to the operator the exact conditions of therespective lines, so that the operator may make no false moves and willnot prematurely disconnect connected lines. There are many objections tothis form of supervisory signaling apparatus, among which may bementioned the disagreeable clicking manifested in the receiver of thecalling subscriber upon the discharge of the condenser occurring whenthe called subscriber removes his telephone.

I also aim to accomplish by means of my invention the avoidance of theobjection arising upon the connection of long lines with short lines,which where double supervision is employed may in some systems create ashunt relation between the subscriberslines, the short line constitutinga shunt of low resistance, preventing the effective operation of thesupervisory signals.

I avoid both of the objections above pointed out by including thesupervisory signals directly in the sides of the circuit including thetelephone-lines, bridge a source of current across the circuit, thebridge being located 'between the supervisory signals, and provideindividual shunts about each supervisory-signal magnet, each shuntcontaining a condenser. Themagnetsofthesurpervisorysignals arepreferably wound sufficiently high to avoid the difficulty thatheretofore arose upon the connection of long and shorttelephonelines,while the provision of separate condensers avoids theobjectionable click in the calling-subscribers ear.

I will explain my invention more fully by reference to the accompanyingdrawing, illustrating the preferred embodiment thereof as applied to asingle switchboard, though the invention is readily adaptable totelephoneexchange systems of other types.

I have shown well-known telephone substation apparatus at substations 90and 120, at each of which is a transmitter a, a primary Winding Z), acallbell c, and a telephone switch-hook d, adapted to complete thebellcircuit or the telephone-circuit under the influence of the receivere. Each telephoneline extends by its limbs to the exchange, each line inthis instance being connected with a spring-jack j'. The limbs of thetelephone-lines terminate at the common battery g, which is preferablyin parallel with the lines, one of the limbs of each line passingthrough the separable contacts of the springjacks and theoperating-magnet 71l of the lineindicator.

I do not wish to be limited to the character of the line-indicator, asany line-indicator maybe employed Without departing from the spirit ofmy present invention. I have indicatedsmall incandescent lamps h',however, to act in this capacity.

The cord-circuit comprises an answeringplugz' and a connecting-plug 7c,united by tip and sleeve strands, with which are connected the springsof a listening-key Z and a ringingkey m for including the operatorstelephone set Z in bridge with the telephone-lines and for connectingthe calling-generator m in circuit with the bell at thecalled-subscribers station. One terminal of the common battery g ispermanently connected with these sides of the telephone-lines that arein this instance connected with the tip line-springs of thespring-jacks. The other terminal of the common battery is connected withthe remainingside of the telephone-lines through the line-indicatorswhen the spring-jacks are free of plugs and is also connected at a pointbetween the magnets n and o with a strand of the cord-circuit-in thisinstance the sleevestrand that unites the long line-springs of thespring-jacks when subscribers are connected for conversation-the helicesof these magnets being thus included in series in the sleevestrand, oneupon eachl side of the bridge connection including the battery. Thebatteryv bridge connection also includes an impedancecoil n2 to preventthe shunting of voice-currents across this bridge. The magnets n and 0may serve to control the supervisory signals in any preferred manner. Iprefer to have these magnets control the supervisory signalselectrically, for which purpose I preferably use supervisoryindicating-lamps 'n' o as the supervisory signals whose circuits arecontrolled by the armatures of the magnets or relays fn and o. There arethus established when a connection is put up between subscribers twocircuits in multiple connection, the bridge including a battery andimpedance being common to these two circuits. In order to prevent onecircuit from acting as a shunt of low resistance to the other, thesupervisory relays or electromagnets n and o are each made ofsufficiently high resistance, one hundred ohms being usually suficientfor each electromagnet.

The supervisory magnets n and 0 are shunted by means of condensersp andq, each magnet having its own shunt-circuit, terminating directly at theterminals thereof, so that the condenser corresponding to thecalling-subscribers telephone-line will not be discharged upon theremovalof the receiver at the calledsubscribers station. The windings ofthe supervisory relays are such as preferably to be of low impedance, sothat the voice-currents may pass through these windings and through thecondensers in parallel, so that if the condensers were in effect notpresent or were disconnected conversation could still be carried on,though obviously this arrange; ment is not so satisfactory.

Having thus described my invention, I claim as new and desire to secureby Letters Patent- 1. In a telephone system, the combination withtelephone-lines extending from substations to an exchange, ofcord-connecting apparatus at the exchange for uniting subscribers forconversation, a bridge placing the ltelephone-lines when connected inshunt-circuit relation, two supervisory signals, each of saidtelephone-circuits including the operating-magnet of a supervisorysignal, a condenser directly in shunt of each supervisory magnet,and asource of current in circuit with the said bridge, substantially asdescribed.

2. In a telephone system, the combination with telephone-lines extendingfrom substations to an exchange, of cord-connecting apparatus at theexchange for uniting subscribers for conversation, a bridge placing thetelephone-lines when connected in shunt-circuit relation, twosupervisory signals, each of said telephone-circuits including theoperatingmagnet of a supervisory signal, a condenser in shunt of eachsupervisory magnet, and a source of' current in the said bridge,substantially as described. v

3. In a telephone system, the combination with telephone-lines extendingfrom substations to an exchange, of cord-connecting apparatus at theexchange for uniting subscribers for conversation, a bridge placing thetelephone-lines when connected in shunt-circuit relation, twosupervisory signals, each of said telephone-circuits including theoperatingmagnet of a supervisory signal, a condenser directly in shuntof each supervisory magnet, and a source of current in circuit with thesaid bridge, the said electromagnets being included in the same side ofthe combined circuit, substantially as described.

4. In a telephone system, the combination with telephone-lines extendingfrom substations to an exchange, of cord-connecting apparatus at theexchange for uniting subscribers for conversation, a bridge placing thetelephone-lines when connected in shunt-circuit relation, twosupervisory signals, each of said telephone-circuits including theoperatingmagnet of a supervisory signal, a condenser directly in shuntof each supervisory magnet,

and a source of current in the said. bridge, the said electromagnetsbeing included in the same side of the combined circuit, substanL tiallyas described.

5. In a telephone system, the combination with telephone-lines extendingfrom substations to an exchange, of cord-'connecting apparatus at theexchange for uniting subscribers for conversation, a bridge placing thetelephone-lines when connected in shunt-V circuit relation, twosupervisory signals, each of said telephone-circuits including theoperating-magnet of a supervisory signal, a con-v denser directly inshunt of each supervisory magnet, a source of current in circuit withthe said bridge, and an impedance in the said bridge, substantially asdescribed.

6. In a telephone system, the combination with telephonelines extendingfrom substa= tions to an exchange, of cord-connecting apparatus at theexchange for uniting subscribers for conversation, a bridge placing thetelephone-lines when connected in shuntcircuit relation, two supervisorysignals, each of said telephone-circuits including the operating-magnetof a supervisory signal, a condenser directly in shunt of eachsupervisory magnet, a source of current in the said bridge, and animpedance in the said bridge, substantially as described.

7. In a telephone system, the combination IIO with telephone-linesextending from substations to an exchange, of cord-connecting apparatusat the exchange for uniting subscribers for conversation, a bridgeplacing the telephone-lines when connected in shuntcircuit relation, twosupervisory signals, each of said telephone-circuits including theoperating-magnet of a supervisory signal, a condenser directly in shuntof each supervisory magnet, a source of current in circuit with the saidbridge, the said electromagnets being included in the same side of thecombined circuit, and an impedance in the said bridge, substantially asdescribed.

8. In a telephone system, the combination with telephone-lines extendingfrom substations to an exchange, of cord-connecting apparatus at theexchange for uniting subscribers for conversation, a bridge placing thetelephone-lines when connected in shuntcircuit relation, two supervisorysignals, each of said telephone-circuits including the operating-magnetof a supervisory signal, a condenser directly in shunt of eachsupervisory magnet, a source of current in the said bridge, the saidelectromagnets being included in the same side of the combined circuit,and an impedance in the saidk bridge, substantially as described.

9. Cord-connectiug apparatus, comprising the two strands of acord-circuit, a bridge, two supervisory relays, one included 'on eachside of said bridge, and a condenser directly in shunt of eachrelaywinding, substantially as described.

In witness whereof I hereunto subscribe lmy name this 12th day ofAugust, A. D. 1901.

WILLIAM M. DAVIS.

Witnesses:

FLORENCE WICK'LIN, GEORGE L. CRAGG.

